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.Dd October 4, 2022
.Dt ZSTREAM 8
.Os
.
.Sh NAME
.Nm zstream
.Nd manipulate ZFS send streams
.Sh SYNOPSIS
.Nm
.Cm dump
.Op Fl Cvd
.Op Ar file
.Nm
.Cm decompress
.Op Fl v
.Op Ar object Ns Sy \&, Ns Ar offset Ns Op Sy \&, Ns Ar type Ns ...
.Nm
.Cm redup
.Op Fl v
.Ar file
.Nm
.Cm token
.Ar resume_token
.Nm
.Cm recompress
.Op Fl l Ar level
.Ar algorithm
.
.Sh DESCRIPTION
The
.Sy zstream
utility manipulates ZFS send streams output by the
.Sy zfs send
command.
.Bl -tag -width ""
.It Xo
.Nm
.Cm dump
.Op Fl Cvd
.Op Ar file
.Xc
Print information about the specified send stream, including headers and
record counts.
The send stream may either be in the specified
.Ar file ,
or provided on standard input.
.Bl -tag -width "-D"
.It Fl C
Suppress the validation of checksums.
.It Fl v
Verbose.
Print metadata for each record.
.It Fl d
Dump data contained in each record.
Implies verbose.
.El
.Pp
The
.Nm zstreamdump
alias is provided for compatibility and is equivalent to running
.Nm
.Cm dump .
.It Xo
.Nm
.Cm token
.Ar resume_token
.Xc
Dumps zfs resume token information
.It Xo
.Nm
.Cm decompress
.Op Fl v
.Op Ar object Ns Sy \&, Ns Ar offset Ns Op Sy \&, Ns Ar type Ns ...
.Xc
Decompress selected records in a ZFS send stream provided on standard input,
when the compression type recorded in ZFS metadata may be incorrect.
Specify the object number and byte offset of each record that you wish to
decompress.
Optionally specify the compression type.
Valid compression types include
.Sy off ,
.Sy gzip ,
.Sy lz4 ,
.Sy lzjb ,
.Sy zstd ,
and
.Sy zle .
The default is
.Sy lz4 .
Every record for that object beginning at that offset will be decompressed, if
possible.
It may not be possible, because the record may be corrupted in some but not
all of the stream's snapshots.
Specifying a compression type of
.Sy off
will change the stream's metadata accordingly, without attempting decompression.
This can be useful if the record is already uncompressed but the metadata
insists otherwise.
The repaired stream will be written to standard output.
.Bl -tag -width "-v"
.It Fl v
Verbose.
Print summary of decompressed records.
.El
.It Xo
.Nm
.Cm redup
.Op Fl v
.Ar file
.Xc
Deduplicated send streams can be generated by using the
.Nm zfs Cm send Fl D
command.
The ability to send deduplicated send streams is deprecated.
In the future, the ability to receive a deduplicated send stream with
.Nm zfs Cm receive
will be removed.
However, deduplicated send streams can still be received by utilizing
.Nm zstream Cm redup .
.Pp
The
.Nm zstream Cm redup
command is provided a
.Ar file
containing a deduplicated send stream, and outputs an equivalent
non-deduplicated send stream on standard output.
Therefore, a deduplicated send stream can be received by running:
.Dl # Nm zstream Cm redup Pa DEDUP_STREAM_FILE | Nm zfs Cm receive No …
.Bl -tag -width "-D"
.It Fl v
Verbose.
Print summary of converted records.
.El
.It Xo
.Nm
.Cm recompress
.Op Fl l Ar level
.Ar algorithm
.Xc
Recompresses a send stream, provided on standard input, using the provided
algorithm and optional level, and writes the modified stream to standard output.
All WRITE records in the send stream will be recompressed, unless they fail
to result in size reduction compared to being left uncompressed.
The provided algorithm can be any valid value to the
.Nm compress
property.
Note that encrypted send streams cannot be recompressed.
.Bl -tag -width "-l"
.It Fl l Ar level
Specifies compression level.
Only needed for algorithms where the level is not implied as part of the name
of the algorithm (e.g. gzip-3 does not require it, while zstd does, if a
non-default level is desired).
.El
.El
.
.Sh EXAMPLES
Heal a dataset that was corrupted due to OpenZFS bug #12762.
First, determine which records are corrupt.
That cannot be done automatically; it requires information beyond ZFS's
metadata.
If object
.Sy 128
is corrupted at offset
.Sy 0
and is compressed using
.Sy lz4 ,
then run this command:
.Bd -literal
.No # Nm zfs Ar send Fl c Ar … | Nm zstream decompress Ar 128,0,lz4 | \
Nm zfs recv Ar …
.Ed
.Sh SEE ALSO
.Xr zfs 8 ,
.Xr zfs-receive 8 ,
.Xr zfs-send 8 ,
.Lk https://github.com/openzfs/zfs/issues/12762
